Fluid-operated drop-forge press

ABSTRACT

A plunger, downwardly accelerated by fluid pressure, enters an oil-filled ram cylinder to drive the ram toward a press bed at relatively reduced speed but with increased force, an air cushion intercepting the piston toward the end of its working stroke to facilitate an elastic stroke reversal. The air cushion may be selectively extended and controlledly vented to act as a brake slowing down the working stroke for deburring or other shaping operations requiring only a fraction of the available ram force.

United States Patent 3,039,439 6/1962 Murek lnventor Hans Beebe Gardeleubergstr 29, 5609 Huckeswagen, Germany Appl. No. 774,259 Filed Nov. 8, 1968 Patented June 15, 1971 Priority Nov. 9, 1967 Germany P 16 27 413.8

FLUID-OPERATED DROP-FORGE PRESS 8 Claims, 3 Drawing Figs.

US. Cl 72/453, 100/269 1nt.Cl B21j 7/24 Field of Search 72/453;

References Cited UNITED STATES PATENTS Compressed Air 54 3,113,476 12/1963 Murek 72/453 3,158,048 11/1964 Bollar 72/453 3,194,049 7/1965 Riemenschneider 72/453 3,277,691 10/1966 Beche 72/453 3,296,853 1/1967 Beche... 72/453 3,352,143 11/1967 Bollar 72/453 3,411,340 11/1968 Asari 72/453 3,427,857 2/1969 Asari 72/453 Primary ExaminerRichard J. Herbst Assistant Examiner-Gene P. Crosby Attorney-Karl F. Ross PAIENTEUJUMSIQH 3,584,498

sum 2 BF 2 .VALVE J CONTROL l l l l I Hans Bch INVEN'IOR.

Attorney FLUID-OPERATED DROP-FORGE PRESS My present invention relates to a fluid-operated drop forge press of the general type described in my prior U.S. Pats. No. 3,277,69i and No. 3,296,853.

Such a press has a ram which confronts a press bed and is reciprocally guided, generally vertically, in a frame rigid with the bed, the ram forming a cylinder for a hydraulic liquid such as oil upon which pressure is exerted by one or more plungers to displace the ram toward the bed. Since the effective area of the plunger or plungers is only a fraction of that of the ram, an advance of the plunger at a given speed results in a working stroke of the ram at reduced speed but with commensurably increased force. The advance of the plunger or plungers also occurs under pressure of a fluid which in my above-identified prior patents is a hydraulic liquid such as that filling the ram cylinder.

l have found that, in such systems, the hydraulic liquid (oil) must sometimes flow at very high velocities, e.g. at or above speeds of 12 meters per second, the need for reversing the fast-moving liquid columns at the end of each working stroke resulting in mechanical difficulties and creating pressure peaks which may be several times the operating pressure of, say, 200 to 300 atmospheres. Other problems arise from the risk that leaky couplings or cracked pipes in the elevated highpressure conduit system may spatter oil' onto the machinery and the personnel, with the added danger of fire and serious injuries if the oil is hot as will usually be the case.

An important object of my invention, therefore, is to provide means in such press for eliminating the use of hydraulic liquids in driving the ram-accelerating plunger or plungers.

Another object is to provide means for so cushioning the plunger advance as to soften the impact upon the press frame and to facilitate an elastic reversal of the plunger stroke.

A further object of this invention is to provide means for selectively adjusting the plunger motion and therefore the ram stroke so that, for certain purposes, the displacement of the ram is slowed in the terminal phase of its working stroke with a resultant reduction in the effective kinetic energy of the moving masses. This is particularly desirable for such preliminary shaping operations as upsetting (e.g. the flatening of tail blanks for descaling purposes and to simplify the subsequent forging work) or performing (e.g. of crankshaft), or for after treatments such as deburring. In all these ancillary operations, it is sufficient to employ only a fraction of the available press energy, e.g. about one-sixth thereof, so that a 1,000-ton or 10,000-ton press need not deliver more than 170 tons or 1700 tons, respectively, for this purpose.

The foregoing objects are realized, pursuant to my present invention, by the provision of a source of gas pressure bearing upon the plunger or plungers for advancing same to initiate the working stroke of the ram, the reversal of the plunger and ram stroked being brought about by counteracting restoring means which may include hydraulically operated pistons similar to those of my above-identified prior patents. A gas cushion, positioned to intercept the plunger or plungers after a predetermined advance thereof and in a terminal phase of the ram stroke, serves as a buffer for elastically reversing the plunger motion.

More specifically, the press frame may form a gas space communicating with a source of gas pressure (e.g. an air compressor) through a connection which is preferably open only in a fully retracted plunger position, an enlarged plunger head being then disposed at a location remote from the entrance of a socket which confines the aforementioned gas cushion and receives the plunger head with small clearance near the end of its forward stroke. For simplicity, and in conformity with the usual arrangement, this forward stroke and the corresponding ram stroke will be assumed hereinafter to be downwardly directed. As the plunger head descends, it enters the gas cushion which is elastically compressedwhile the working stroke of the ram continues under the momentum of the moving masses. After the kinetic energy of these masses has been dissipated in the deformation of the workpiece, the compressed gas (generally air) in the socket initiates a reversal of the plunger movement which is then accelerated by the hydraulic restoring force acting preferably directly upon the ram, e.g. under the control of a timer tripped by a pedal as shown in my prior patents. The ascent of the plunger head may be similarly cushioned by a sleeve having one or more pressure-equalizing orifices which are at least partly blocked by the plunger head as it approaches its retracted position.

According to another important feature of my invention, the socket constituting the gas cushion has an outlet in the form of one or more ports which can be selectively obstructed and, when unblocked, vent the interior of the socket at a controlled rate so that the cushion acts as a brake slowing down the working stroke for the aforementioned ancillary operations. in a particularly advantageous embodiment, a first port disposed at a higher level, thus closer to the socket entrance, communicates with the gas space by way of a normally open first valve while a lower second port opens into the surrounding atmosphere via a normally closed second valve, the positions of these valves being automatically reversed (if an associated control is operated) as soon as the plunger head enters the socket. Closure of the first valve effectively extends the length of the socket so that a larger part of the downward stroke is subjected to the braking force exerted by the throttled escape of the gas through the second port.

The invention will be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a sectional elevation of a press according to the invention;

FIG. 2 is a view similar to FIG. 1, showing a modification; and

HO. 3 is a fragmentary view illustrating part of the assembly of F IG. 2.

The press shown in FIG. 1 is similar in many respects to the one disclosed in my prior U.S. Pat. No. 3,296,853 and comprises a frame 1 rigid with a bed 13 which supports a stationary lower die 14 cooperating with a movable upper die 15 suspended from a ram 2. The upper part of the ram is slidably guided for vertical reciprocation in a cylindrical neck 3 of frame 1 and, in its turn, forms an upwardly open cylinder 19 for hydraulic fluid. A tubular insert 4 extends from above into the cylinder 19 and forms a guide channel 16 for a plunger 18 which is vertically reciprocable in a housing 17 rising from the neck 3, this housing defining an air space 51 which communicates through a passage 52 with an air compressor not shown. The connection 52 includes an inlet valve 53 having a projecting pin 54 which, upon a return of plunger 18 to its illustrated top position, is repressed against the force of a spring 55 to allow air under pressure to enter a clearance 56 above the plunger head 50 within a sleeve 57 closely surrounding the head. Several pressure-equalizing orifices 58a, 58b, 580 are disposed at different levels in sleeve 57, the top orifice 58a and part of the next-lower orifice 58b being obstructed by the retracted piston head. in the example here assumed, the inlet pressure prevailing in space 56 may have a magnitude of 14 atmospheres gauge. A branch line 52a from valve 53 to space 51 bypasses the sleeve 57.

A socket 59 at the top of insert 4 forms an air cushion 60 to intercept the head 50 at the end of the descent of plunger 18. The relative volume of plunger 18 and space 51 may be so chosen that, as the head 50 moves from its illustrated retracted position into its bottom position within socket 59, the air pressure within that space diminishes only moderately, e.g. from the original 14 atmospheres to 11 atmospheres; the resulting expansion entrains a slight lowering of the air temperature, e.g. from 20C to about 5C. Upon the subsequent stroke reversal, the original pressure and temperature are restored so that the system will not overheat. The source connected to inlet 52 only has to replenish air losses due to leakage. No additional hydraulic liquid needs to be supplied during the normal operation of the machine. At 29 there is shown one of the two side openings serving for the introduction of the workpiece.

The ram 2 is directly connected with a pair of piston rods 6 which terminate in pistons 7 within the base of the frame 1. Two such pistons have been shown although, of course, several pairs could be provided. Pistons 7 slide in sockets 8 which are connected, via tubes 9, with a distributor 34 disposed beneath the bed 13. The distributor, operating for example under the control of a pedal-actuated timer, alternately admits oil under pressure to cylinders 8 and drains these cylinders in a manner fully disclosed in my prior patents and therefore not further illustrated here. When the pipes 9 are connected to the sump or low-pressure side of the oil supply, plunger 18 is free to descend in response to the air pressure in space 51 hydraulically drives the ram 2 downwardly at a rate determined by the ratio of the outer diameters d and D of the plunger and the ram, the speed ratio being proportional to the ratio of the areas, i.e. to d /D The ram and, therefore, the pistons 7 attain velocities which, toward the end of the working stroke, may be about two meters per second; upon the subsequent return stroke, occurring when the distributor 34 readmits oil under pressure to the cylinders 8, this speed may be about 0.6 to 0.8 meters per second. As the plunger 16 may move at about six to seven times that speed, it will be apparent that the energy of the moving oil column in my improved press (proportional to the square of the velocity) is only about H150 to 1/200 of the energy developed with oil-driven plungers. In fact, the plunger may be safely accelerated to about 20 meters per second without overtaxing the hydraulic system. The descent of plunger head 50 is arrested as soon as the air drop within socket 50 is sufficiently compressed to balance the pressure of the expanded air in space 51, e.g. of 11 atmospheres. At this point, the upper die will have moved close enough to the lower die 14 to deform an interposed workpiece to the desired extent. Toward the end of the return stroke, head 50 increasingly compresses the air trapped within sleeve 57 as it successively cuts off the escape of that air through the various orifices 58c, 58b, 58a. The cycle is then repeated as the pin 54 reconnects the air supply with clearance 56 and the distributor 34 operates to drain the cylinders 8.

The press shown in FIGS. 2 and 3 is generally similar to that of FIG. 1, corresponding elements having been designated by the same reference numerals and requiring therefore no further description. Socket 59', however, has been extended upwardly so that its air cushion 60' intercepts the descending head 50 earlier in the cycle. Normally, the upper part of this air cushion is made ineffectual on account of an outlet port 61 which communicates via a passage 63 with the air space 51, the passage 63 including a valve 64 shown open in FIG. 2. A second, lower port 62, normally closed by a valve 65, leads to the surrounding atmosphere. Thus, with the valve position illustrated in FIG. 2, the press operates essentially in the manner described in connection with FIG. 1.

FIG. 3 shows an alternate position of valves 64 and 65, the former being closed to increase the effective length of socket 59' while the latter is open to vent the air cushion 60' to the atmosphere. This reversal is brought about by a control circuit 66, FIG. 2, which in the closed position of a manual switch 67 responds to the tripping of a switch 68 by a cam 69 on one of the rods 6. The position of cam 69 is so chosen that, with switch 67 closed, valves 64 and 65 are reversed at the instant when head 50 enters the socket 59, as shown in FIG. 3. Thus, space 51 never communicates directly with the outer atmosphere and only a small volume of air is lost from it through the open valve 65, this amount being easily replenishable by the supply 52 upon the next ascent of the plunger 18.

Thus, if the operator closes the selector switch 67, air cushion 60 acts as a brake upon the descending plunger while the air thereof escapes at a throttled rate through the port 62. The ram 2, therefore, approaches its bottom position with reduced kinetic energy to perform an ancillary operation (e.g. upsetting, performing or deburring) as described above. Controller 66 restores the valves 64, 65 to the position of FIG. 2 upon reclosure of switch 68 by the ascending cam 69, or in response to some other signal, before the head 50 leaves the socket 59.

With a total ram stroke of, say, 250 mm., the retarding effect of cushion 60' may be exerted over about one-fifth of the stroke, i.e. a path length of approximately 50 mm. With a speed and stroke ratio of 1:6 between ram 2 and plunger 18, the height of socket 59' will then be about 300 mm., the length of the plunger stroke being approximately 1500 mm.

The retardation of the plunger 18 in the braking position of FIG. 3 may be so chosen, by a suitable dimensioning of socket 59 and outlet 62, that the ram energy exerted upon the workpiece is only about one-sixth, or 17 percent, of the total energy available in the valve position of FIG. 2.

Thus, the arrangement of FIGS. 2 and 3 enables selective operation with either an elastic reversal of the plunger stroke, resulting in elastic lifting of the ram after deformation of the workpiece, or a damped descent followed by a return stroke under the hydraulic control of distributor 34 in response to a signai from a timer or from the operator. The same press, therefore, can be used for drop-forging work and for preliminary or finishing operations with only a minor readjustment of the controls, i.e. opening and closure of selector switch 67.

Since the hydraulic liquid circulates only at the bottom of the installation, all oil lines may be disposed beneath the floor.

Iclaim:

l. A fluid-operated press comprising a frame forming a bed adapted to support a workpiece; a ram confronting said bed while being reciprocably guided on said frame for deforming such workpiece, said ram being formed with a cylinder adapted to receive a hydraulic liquid; plunger means disposed in a passage communicating with said cylinder for exerting pressure upon said hydraulic fluid to displace said ram toward said bed, said plunger means having an effective area substantially less than that of said ram whereby an advance of said plunger means at a given speed results in a working stroke of said ram at reduced speed; a source of gas pressure bearing upon said plunger means for advancing same to initiate said working stroke; restoring means counteracting said gas pressure for reversing the motion of said plunger means and causing a return stroke of said ram; and buffer means forming a gas-cushion socket positioned to intercept said plunger means after a predetermined advance thereof and in a terminal phase of said working stroke for elastically reversing the motion of said plunger means.

2. A press as defined in claim 1 wherein said frame forms a gas space having a connection with said source, said plunger means being provided with a head received in said gas space, said socket being positioned in said gas space and open toward said head to receive the latter with small clearance.

3. A press as defined in claim 2 wherein said socket is provided with restricted outlet means for bleeding the interior thereof under pressure from said head.

4. A press as defined in claim 3, further comprising blocking means for selectively obstructing said outlet means.

5. A press as defined in claim 4 wherein said outlet means forms a first port relatively close to the entrance of said socket and a second port relatively remote from said entrance, said first port communicating with said gas space, said second port opening into the surrounding atmosphere, said blocking means including a normally open first valve in said first port and a normally closed second valve in said second port.

6. A press as defined in claim 5 wherein said blocking means further includes selectively deactivable ram-controlled means for closing said first valve and opening said second valve upon entry of said head into said socket.

7. A press as defined in claim 2 wherein said connection is provided with a normally closed inlet valve disposed to be opened by said head in a fully retracted position thereof for establishing communication between said source and said gas space.

hind said head, said sleeve being provided with at least one pressure-equalizing orifice positioned to be blocked by said head approaching said retracted position. 

1. A fluid-operated press comprising a frame forming a bed adapted to support a workpiece; a ram confronting said bed while being reciprocably guided on said frame for deforming such workpiece, said ram being formed with a cylinder adapted to receive a hydraulic liquid; plunger means disposed in a pAssage communicating with said cylinder for exerting pressure upon said hydraulic fluid to displace said ram toward said bed, said plunger means having an effective area substantially less than that of said ram whereby an advance of said plunger means at a given speed results in a working stroke of said ram at reduced speed; a source of gas pressure bearing upon said plunger means for advancing same to initiate said working stroke; restoring means counteracting said gas pressure for reversing the motion of said plunger means and causing a return stroke of said ram; and buffer means forming a gas-cushion socket positioned to intercept said plunger means after a predetermined advance thereof and in a terminal phase of said working stroke for elastically reversing the motion of said plunger means.
 2. A press as defined in claim 1 wherein said frame forms a gas space having a connection with said source, said plunger means being provided with a head received in said gas space, said socket being positioned in said gas space and open toward said head to receive the latter with small clearance.
 3. A press as defined in claim 2 wherein said socket is provided with restricted outlet means for bleeding the interior thereof under pressure from said head.
 4. A press as defined in claim 3, further comprising blocking means for selectively obstructing said outlet means.
 5. A press as defined in claim 4 wherein said outlet means forms a first port relatively close to the entrance of said socket and a second port relatively remote from said entrance, said first port communicating with said gas space, said second port opening into the surrounding atmosphere, said blocking means including a normally open first valve in said first port and a normally closed second valve in said second port.
 6. A press as defined in claim 5 wherein said blocking means further includes selectively deactivable ram-controlled means for closing said first valve and opening said second valve upon entry of said head into said socket.
 7. A press as defined in claim 2 wherein said connection is provided with a normally closed inlet valve disposed to be opened by said head in a fully retracted position thereof for establishing communication between said source and said gas space.
 8. A press as defined in claim 2 further comprising a guide sleeve in said gas space surrounding said head in a retracted position thereof, said connection opening into said sleeve behind said head, said sleeve being provided with at least one pressure-equalizing orifice positioned to be blocked by said head approaching said retracted position. 